High strength titanium alloys

ABSTRACT

A titanium base alloy comprising 6.3 - 11.0 percent vanadium, 1.75 - 3.3 percent aluminum, 0.75 - 2.25 percent iron, up to 2.25 percent chromium, up to 1.25 percent cobalt, up to 2.25 percent tin, up to 2.25 percent zirconium, up to 0.2 percent oxygen, balance titanium; the total of aluminum plus one half zirconium being between 2.25 percent and 3.25 percent, the ratio of iron to aluminum being no greater than about 1:1 and the maximum of iron plus cobalt being 2.25 percent.

United States Patent [191 Parris et al. 1

1451 Apr. 9, 1974 HIGH STRENGTH TITANIUM ALLOYS [73] Assignee: Titanium Metals Corporation of America, West Caldwell, NJ.

221' Filed: Apr. 18,1972

21 Appl.No.: 245,177

[52] US. Cl. 75/l75.5

[51] Int. Cl. C22c 15/00 [58] Field of Search 75/1755; 148/32, 133, 148/127, 11.5 F

[56] References Cited UNlTED STATES PATENTS 3,615,378 10/1971 Bomberger 75/l75.5

2,804,409 8/1957 Kessler et al. 75/l75.5 X

2.819.959 1/1958 Abkowitz et a1 75/l75.5

2,884,323 4/1959 Abkowitz ct al..... 75/l75.5

2,892.706 6/1959 Jaffee et al. 75/175;

4/1969 Bomberger et al. l48/l2.7 3/1972 Heitman 75/175.5

OTHER PUBLICATIONS Nuclear Science Abstracts, Vol. 22 No. 3. Feb. 15, 1968, Abst. No. 4762 & 4763.

Primary Emminer-Charles N. Lovell Attorney, Agent, or FirmWebb, Burden, Robinson &

Webb

[57] ABSTRACT A titanium base alloy comprising 6.3 11.0 percent vanadium, 1.75 3.3 percent aluminum, 0.75 2.25 percent iron, up to 2.25 percent chromium, up to 1.25 percent cobalt, up to 2.25 percent tin, up to 2.25 percent zirconium, up to 0.2 percent oxygen, balance titanium; the total of aluminum plus one half zirconium being between 2.25 percent and 3.25 percent, the ratio of iron to aluminum being no greater than about 1:1 and the maximum of iron plus cobalt being 2.25 percent.

3 Claims, No Drawings 1 HIGH STRENGTH TITANIUM ALLOYS This invention relates to high strength titanium base alloys and more particularly to titanium base alloys including vanadium, aluminum and iron as essential constituents with other elements included optionally. Various elements are included in the alloy in specified relationships which are set forth hereinafter.

Articles made from alloys within the composition range of our invention are deep hardenable and have high room temperature strength, good ductility, good notch strength and fracture toughness. The articlesare age hardenable and heat treatable to high strength in thick sections. Additionally, the parts have good resistance to plane strain fracture.

In modern technology it is important to combine high strength with good ductility and good fracture toughness. For example, a metal which is not resistant to plane strain fracture may fail under stress due to the presence of a finite crack which is so small that it cannot be seen even in the presence of a dye penetrant. In order to obtain a high strength article, the alloy must The base composition of our novel alloy consists essentially of 6.3 l 1% V, 1.75 3.3% Al. 0.75 2.25% Fe, balance titanium with a maximum oxygen content of 0.2 percent. The total amount of oxygen plus other incidental impurities should not exceed 0.35 percent. The iron to aluminum ratio in the alloy should not exceed about l:l. Our alloy may optionally include up to 2.25 percent chromium, up to 1.25 percent cobalt, up to 2.25 percent tin and up to 2.25 percent zirconium. When zirconium is present in the alloy, the total of aluminum plus one half the zirconium will be between 2.25 percent and 3.25 percent. When cobalt is present in the alloy, the percent of cobalt plus the percent of iron should not exceed 2.25 percent since the cobalt replaces an equivalent amount of iron in the composition. Additionally, when chromium is included in the alloy, it should generally replace an equal amount of vanadium.

Table I shows a number of nominal titanium base alloy compositions, both within and outside the range of our invention, together with heat treatments and the results of metallurgical tests performed on these alloys.

TABLE I TENSILE AND PLANE STRAIN TOUGHNESS PROPERTIES, TENSILE PROPERTIES TRANSVERSE, K DATA FOR CRACK PROPAGATING IN DIRECTION OF ROLLING Composition UTS YS Lo El El K Heat V Fe Al Other Heat Treatment" Ksi Ksi Ksi/ V in.

4505 I 2 3 As Rolled+l000F-4Hr-AC I86 I81 20 9 51.6 do. do. do. do. l425F-l/4Hr-AC+l000F-4Hr-AC I94 187 I5 3 49.7 4543 I0 2 3 As RoIIed+950F-4Hr-AC l8l I70 30 I0 50.] do. do. do. do. I400F-l/2Hr-AC-l-950F-8Hr-AC 179 I71 8 52.3 do. do. do. do. l400F-l/2Hr-AC+l000F-2Hr-AC I78 I70 9 55.3 4550 I0 3 2 As Rolled+950F-8Hr-AC I80 I76 10 32.6 do. do. do. do. l400F-l/2I-Ir-AC+l000F-lHr-AC I98 I94 10 4 31.3 455l l0 2 2 l4OOF-I/2Hr-AC+IO0OF- l Hr-AC I84 I75 10 2 45.3 4552 I0 3 3 l400F-l/2Hr-AC+I lOOF-lHr-AC I64 I59 25 I4 67.6 4554 I0 2 3 lZr As Rolled+950F-8l-lr-AC l9l I85 30 12 37.2 do. do. do. do. do. I400F-I/2Hr-AC+lO5OF-lI-Ir-AC I80 I72 20 8 44.2 4555 I0 2 3 .lZr l400F- l l2Hr-AC-l-950F-4HnAC I94 184 20 7 43 .0 4556 10 1 3 lCo I400F-ll2Hr-AC-l-9OOF-8I-Ir-AC I98 I90 2O 6 38.8 4557 10 l 3 lCo-. l Zr I400F- l /2Hr-AC+900F-8Hr-AC 200 191 20 8 40.1 4506" 7 2 2 2Cr-2Sn-2Zr As Rolled+ll00F-2Hr-AC I87 I86 l0 6 57.6 do. do. do. do. do. do. do. l375F-lIZHr-AC-l-IOSOF-ZHr-AC I87 I79 10 7 58.4

(I) As rolled from I400F.

(2) 0.275" Plate finish rolled it I450F. all others, 0.325 plate finish rolled at HOOF.

have sufficient fracture toughness to prevent failure in the presence of microscopic flaws. The alloys of our in- I vention have this capability.

It is known in the art that the addition of beta stabilizers to a titanium base alloy results in good response to heat treatment and imparts high strength to the alloy. Additionally, it is known that the heat treatability and depth of hardening of an alloy increase in proportion to the amount of retained beta phase after quenching the alloy to room temperature. While the alloys of our invention follow these basic principles, it should be un-' derstood that we have discovered novel alloying combinations as discussed hereinafter. We have further discovered that direct aging of hot worked articles made from the novel alloys of ourinvention provides high ductility at ultimate strength to density ratios exceeding l,l00,000 inches. Our alloys have good fracture toughness even after solution treating in the alpha-beta field followed by aging.

A comparison of the data in Table I shows that Heat .4506 has the highest combination of yield strength and 1:1 and by maintaining the aluminum plus one half the zirconium in the range of 2.25 percent to 3.25 percent.

This can be seen by comparing the results of Heat 4550, wherein the iron to aluminum ratio is 3:2, and the results of Heats 4505 and 4543, wherein the iron to aluminum ratio is 2:3. Results of Heats 4543, 4555 and 4554 illustrate the effects of aluminum plus one half zirconium. These composition limitations may be seen more clearly in Table 11. In Table 11 the linear least squares analysis trend line values for K for various heats were calculated and are compared with observed K values. This data shows that an increase of the iron to aluminum ratio above 1:1 reduces the K below expected values by at least K51 m. as does allowing the total of aluminum plus one half the zirconium to be outside the range of 2.25 percent to 3.25 percent.

It will also be seen from Table 11 that substitution of one cobalt for 1 percent iron as well as the addition of 0.1 percent zirconium results in an alloy having observed results close to the trend line.

TABLE II PLANE STRAIN TOUGHNESS VALUES OBSERVED AND TREND LlNE (1) Calculated from linear least squares of solution treat plus age data given in Table 1: K 185.42 0.7676 YS As stated, the best K performance is obtained by substituting 2 percent chromium for 3 percent vanadium and 2 percent tin plus 2 percent zirconium for 1 percent aluminum in the basic Ti-10V-2Fe-3Al alloy. The preferred compositions of our novel alloy are the basic Ti-10V-2Fe-3A1 alloy and Ti-7V-2Cr-2Fe-2A1- 2Sn-2Zr. In both of these alloys, the preferred maximum oxygen content is 0.11 percent although oxygen may be present up to 0.2 percent. The total of oxygen and the other interstitials, carbon and nitrogen. may be present up to 0.35 percent.

In many applications the ability of a metal product to retain high strength in the presence of a machined notch is important. Table 111 shows the results of tests on 9% inch round bars finish rolled from 1,400F and then subjected to high stress in the presence of ma chined notches. The alloys of our invention which exhibit good toughness as shown by the K values also have high notch strength. The notch tensile strength of the preferred Ti-7V-2Cr-2Fe-2A1-2Sn-2Zr is higher than the yield strength even when the yield strength is in excess of 200 Ksi. Additionally, Table 111 shows the effect of thermomechanical processing history on the properties of alloys within the scope of our invention. The effect is particularly evident from a consideration of the reduction of area values. Values of about percent are typical when the alloys are rolled from 1,400F and then aged directly to a yield strength within the range of 160 180 Ksi.

it is also shown in Table 111 that, when finished rolled from 1,400F, the basic Ti-10V-2Fe-3Al alloy is flexible with regard to subsequent heat treatment. This is an important commercial feature of our alloy since microstructure control is not always possible throughout heavy sections in industrial practice. For this reason, if solutionizing should occur in one portion of a large section of our alloy before the rest of that section is finished forged, the properties will still be uniform after aging. Known high strength commercial titanium base alloys donot include this feature.

1 TABLE 111 TENSlLE AND NOTCH TENSILE PROPERTIES OF l/2" ROUND Composition UTS YS RA EL NTS" Heat V Fe A1 Other Heat Treatment Ksi Ksi Ksi 4550 10 3 2 As Rol1ed-i-950F-4Hr-AC 185 181 56 11 237 do. do. do. do. As Rolled-i-lOOOF-ZHr-AC 179 176 57 17 236 do. do. do. do. As Ro1led+1050F-1Hr-AC 162 160 56 17 234 do. do. do. do. '140OF- l /2Hr-AC+950F-4Hr-AC 202 194 15 y 9 do. do. do. do. 140OF-1/2Hr-AC+l000F-2Hr-AC 186 177 29 6 229 do. do. do. do. 1400F-1/21-1r-AC-1-1050F-1Hr-AC 164 158 40 14 221 4551 10 2 2 As Ro11ed+950F-4Hr-AC 154 153 19 238 do. do. do. do. OF-1/2Hr-AC+9$OF-4Hr-AC 192 186 9 3 4552 10 3 3 As Ro11ed+950F-8Hr-AC 179 179 41 15 255 do. do. do. do. As Ro11ed+1000F-4Hr-AC 172 172 56 18 244 do. do. do. do. As Rolled+1050F-2Hr-AC 174 172 52 14 243 do. do. do. do. 14OGF-1/2Hr-AC+950F-8Hr-A 21-2 210 6 4 133 do. do. do. do. 1400F-1/2Hr-AC+1000F-4Hr-AC 210 205 8 2 150 do. do. do. do. 1400F-1/2Hr-AC+1050F-2Hr-AC 196 192 13 5 190 4553 10 2 3 As Rolled-+950F-8Hr-AC 179 176 55 16 242 do. do. do. do. As Ro11ed+l00OF-4Hr-AC 173 57 17 241 do. do. do. do. As Rolled-l-lOSOF-ZHr-AC 166 164 55 18 248 do. do. do. do. 1400F-1/2Hr-AC-l-950F-81-1r-AC 177 170 55 17 211 do. do. do. do. 1400F-1/21-1r-AC-t-1000F-4Hr-AC 183 173 40 15 228 do. do. do. do. 1400F-1/2Hr-AC-l 1050F-2Hr-AC 174 167 46 14 219 4554 10 2 3 121' As Ro11ed+950F-4Hr-AC 185 182 51 19 234 do. do. do. do. do. As Rolled-l-IOOOF-ZHr-AC 179 44 15 237 do. do. do. do. do. As Rol1ed+l050F-1Hr-AC 171 168 45 16 226 do. do. do. do. do. 1400F-1/21-1r-AC+950F-4Hr-AC 200 189 17 8 161 do. do. do. do. do. 1400F-IIZHr-AC-HOOOF-ZHr-AC 191 183 17 7 186 do. do. do. do. do. .14OOF-1/2Hr-AC+105OF-1Hr-AC 192 184 25 12 196 4555 10 2 3 .1Zr As Rol1ed+950F-4Hr-AC 177 I74 58 19 242 do. do. do. do. do. As Rolled-l-lOOOF-2Hr-AC 166 164 60 19 240 do. do. do. do. do. As Ro11ed+1050F-lHr-AC 162 161 60 21 233 do. do. do. do. do. 1400F-1/2Hr-AC-i-9SOF-4Hr-AC 188 179 31 1 1 228 do. do. do. do. do. 1400F-1/2Hr-AC+1000F-2Hr-AC 176 169 52 16 214 do. do. do. do. do. 1400F-1/2Hr-AC+1OSOF-1Hr-AC 175 169 51 16 225 4556 10 1 3 1C0 As Rol1ed+950F-8Hr-AC 170 169 61 20 234 do. do. do. do. do. As Rolled+1000F-4Hr-AC 163 163 65 22 236 do. do. do. do. do. 158 156 61 17 232 Ill Continued TENSlLE AND NOTCH TENSlLE PROPERTIES OF l/2" ROUND Composition UTS YS RA EL NTS" Heal V Fe AI Other Heat Treatment Ksi Ksi Ksi do do. do. do. do 1400F-1/2Hr'AC'P950F-8Hr-AC 176 171 56 17 230 do do. do. do. do. 1 F-1/2Hr-AC+1000F-4Hr-AC I73 167 49 16 229 do do. do. do. do. MOOF-1/2Hr-AC+1()5OF-2Hr-AC 170 164 58 21 234 4557 1 3 1Co-.1Zr As Rolled-i-JSOF-BHr-AC 170 169 54 17 240 do. do. do. do do. do As Ro1led+1000F-4Hr-AC 167 167 59 235 do. do. do. do do. do As Rolled+l050F-2Hr-AC 159 158 63 20 235 do. do. do. do do. do l400F-l/2Hr-AC+950F-8Hr-AC I79 176 42 14 238 do. do. do. do do. do 1400F-1/2Hr-AC+1000F-4Hr-AC 175 172 32 13 232 do. do. do. do do. do l400F-l/2Hr-AC+l050F-2Hr-AC 166 163 56 18 222 4505" 10 2 3 As Rolled-HOOOF-Zl-lr-AC 184 180 51 16 248 do. do. do. do. As Rolled-+1000F-4Hr-AC 177 174 54 16 248 do do. do. do. 1450F-l/4Hr-AC+1000F-2Hr-AC 192 183 20 9 218 do. do. do. do. 1450F-l/4Hr AC+1000F-4Hr-AC 188 183 10 214 450 7 2 2 2Cr-2Sn-2Zr As Rol1ed+l000F-4Hr-AC 208 204 27 12 248 do. do. do. do. do. do. do. As Rolled+lO00F-8Hr-AC 208 205 32 13 232 do. do. do. do. do. do. do. l450F-1/4Hr-AC+l0O0F-4Hr-AC 216 211 7 5 215 do. do. do. do. do. do. do. 1450F-1/4Hr-AC+1000F-8Hr-AC 210 200 9 5 219 (l) NOlCh acuity factor K,=8. (2) Finish rolled above beta lransus, all others finished rolled below beta transus.

The alloys of our invention may be made by the conventional industrial technique of compacting sponge blended with the basic or master alloy, melting and remelting the blend in a vacuum or in an inert gas atmosphere followed by forming operations such as forging, rolling, drawing, etc. into the desired semi-finished product. The semi-finished product is then heat treated as necessary to enable finishing and material application. It will be found that the alloys of our invention are useful in the manufacture of aerospace vehicles and in other environments which require a high strength to density ratio.

While we have shown and described preferred embodiments of our invention, it should be understood that our invention may otherwise be embodied within the scope of the appended claims.

We claim:

1. A titanium base alloy consisting essentially of 6.3 11.0 percent vanadium, 1.75 3.3 percent aluminum,

0.75 2.25 percent iron, up to 2.25 percent chromium, up to 1.25 percent cobalt, up to 2.25 percent tin, up to 2.25 percent zirconium, up to 0.2 percent oxygen, balance titanium, the ratio of iron to aluminum in said alloy being no greater than about 1:1 and the total of the iron and the cobalt being not greater than 2.25 percent, the foregoing quantities being in terms of weight percent.

2. An alloy according to claim 1 consisting of 10 per cent vanadium, 2 percent iron and 3 percent aluminum.

3. An alloy according to claim 1 consisting of 7 percent vanadium, 2 percent iron, 2 percent aluminum and including 2 percent chromium, 2 percent tin and 2 percent zirconium, said alloy characterized by a K fracture toughness of at least 35 Ksi/ Vin.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 802, 877 Dated April 9, 1974 Inventor(s) Warren M. Parris and Harry W. Rosenberg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

, In Table I after Footnote (2) insert the following:

--(3) Elongation to fracture of 0. 2 inch length that includes the Fracture.

- -(4) Total elongation over 1 inch gage length.

Signed and sealed this 30th day of July 1971+.

(SEAL) Attest:

McCOY M. GIBSON,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC4050 uscoMM-Dc 60376-P69 V 7' V M I w u.s eovsnmupn rnnmus ornc; "l9 c ase-s34. 

2. An alloy according to claim 1 consisting of 10 percent vanadium, 2 percent iron and 3 percent aluminum.
 3. An alloy according to claim 1 consisting of 7 percent vanadium, 2 percent iron, 2 percent aluminum and including 2 percent chromium, 2 percent tin and 2 percent zirconium, said alloy characterized by a KIC fracture toughness of at least 35 Ksi/ Square Root in. 